Rollbit has great reward system indeed but I think their referral system is really bad (at least on the lowest level).
I invited my friend to play, he wagered $165 000 and I got only like $170 commission, when on most other sites that would've been at least 350-400+
Of course, Rollbit has a good prize system where players win more prizes due to their luck. I saw a guy yesterday who bet $250 from Razor returned, and won $50,000 in 200x multiplier. It was really the biggest prize for the person who won a big bet, Rollbit offers really great prizes. But if the percentage of referral bonus is low then it is not bad, but it is a trustworthy gambling platform. Also, if you invite your friend to a gambling platform, if that platform cheats, then everything will be lost. So I think you should be satisfied with the fact that you invited your friend to a trusted platform, and you got a small referral bonus.